US6195870B1 - Compressive annealing of superconductive tapes - Google Patents
Compressive annealing of superconductive tapes Download PDFInfo
- Publication number
- US6195870B1 US6195870B1 US09/249,476 US24947699A US6195870B1 US 6195870 B1 US6195870 B1 US 6195870B1 US 24947699 A US24947699 A US 24947699A US 6195870 B1 US6195870 B1 US 6195870B1
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- tape
- superconductive
- oxide superconductive
- high temperature
- pressure
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N60/00—Superconducting devices
- H10N60/01—Manufacture or treatment
- H10N60/0268—Manufacture or treatment of devices comprising copper oxide
- H10N60/0801—Processes peculiar to the manufacture or treatment of filaments or composite wires
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49014—Superconductor
Definitions
- the present invention relates to superconductive tapes and more particularly to superconductive tapes prepared under low pressure compressive annealing. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).
- a general process of fabricating superconductive tape involves initially preparing a superconductive powder, filling a tube or pipe of silver with the superconductive powder, sealing the pipe or tube, subjecting the pipe or tube to reducing or deforming operations to form tape, and finally sintering the reduced tape at high temperatures.
- thermomechanical processing methods have been largely unsuccessful in improving the critical current density, J c , of BSCCO superconducting tapes.
- Limited current density remains an obstacle in the commercial application of BSCCO high temperature superconductors.
- Conventional processing involves iterative cycles of mechanical deformation to develop texture and reduce porosity followed by thermal annealing to react components, to relieve stress and to heal microcracks caused by the deformation. Texture and deformation hardening and cracking may limit the ability to obtain the desired grain texture through deformation alone.
- the oxide core density of the superconductive tapes decreases during the annealing, causing J c to decrease as well.
- the present invention provides a process of preparing a high temperature oxide superconductive tape including heating an oxide superconductive precursor tape at ambient pressure and at temperatures of from about 810° C. to about 840° C. for a sufficient period of time, pressing said oxide superconductive precursor tape under high pressure of greater than about 0.1 GPa at ambient temperature, and heating said oxide superconductive precursor tape under low compressive uniaxial pressures insufficient to deform said oxide superconductive precursor tape at temperatures of from about 810° C. to about 840° C. for periods of time from about 100 hours to about 200 hours.
- the high temperature oxide superconductive tape includes a bismuth-strontium-calcium-copper oxide as the superconductive material.
- FIG. 1 shows a press useful in applying the low compressive pressures on the superconductive tapes during processing in accordance with the present invention.
- FIG. 2 shows the fraction of ⁇ / ⁇ max caused by each superconductive phase where the ratio can be roughly considered as the volume fraction of that phase with respect to the total amount of superconducting phases as measured by a SQUID.
- the present invention is concerned with preparation of superconductive tapes such that the superconductive tapes have enhanced critical current densities.
- superconductive tapes are annealed under uniaxial low pressures. Such a process promotes texture formation, enhances formation kinetics of the superconducting phase and prevents de-sintering of the oxide superconductive material. Results of superconductive tapes prepared under such a low pressure compressive annealing have shown significant improvement in critical current density. Additionally, the present process can avoid the multiple step iterative cycles of mechanical deformation followed by thermal annealing and thus reduce processing time and costs.
- uniaxial is meant that the pressure is applied in a single axial direction.
- the single axial direction is generally perpendicular to the surface of the superconductive tapes.
- the process employs low compressive pressure or stress on the superconductive tape during the entire annealing process to develop superconductive phase and texture.
- the process differs from hot pressing and hot rolling in that such hot pressing and hot rolling employ a large compressive/shear stress to deform the tape in a short period to mechanically increase the density and the texture and then no pressure is used during the subsequent thermal annealing during which time the density and texture may be decreased.
- low compressive pressure is generally meant a pressure that does not result in measurable deformation of the superconductive tapes. Generally, such pressures can be in the range of from about 1 MPa to about 25 MPa, preferably from about 1 MPa to about 15 MPa.
- FIG. 1 shows a press useful in applying the low compressive pressures on the superconductive tapes during processing in accordance with the present invention.
- Apparatus 10 shows three plates 12 , 14 , and 16 with individual pairs of the plates separated by a roller 18 or 20 as shown. This design is effective in maintaining uniform pressure on the tape samples (shown as 22 and 24 ).
- thermomechanical processing technique of this invention can be used for processing of superconductive tapes or may be used for the joining together of multiple superconductive tape pieces.
- the present superconductive article generally includes a high temperature oxide superconductive material such as a high temperature superconductive oxide.
- a high temperature oxide superconductive material such as a high temperature superconductive oxide.
- high temperature is generally meant that such a material exhibits superconductivity at temperatures above about 35 K, and preferably exhibits superconductivity at the temperature of liquid nitrogen, about 78 K.
- a superconductive oxide core can be prepared from bismuth-based superconductive materials such as a bismuth-strontium-calcium-copper oxide, e.g., Bi 2 Sr 2 Ca 2 Cu 3 O x (Bi-2223) or Bi 2 Sr 2 Ca 1 Cu 2 O x , (Bi-2212) (x being well known to those skilled in the art)or a bismuth-lead-strontium-calcium-copper oxide, e.g., (Bi 2 ⁇ x Pb x )Sr 2 Ca 2 Cu 3 O x (x being well known to those skilled in the art), from rare earth-based superconductive materials including yttrium-based superconductive materials such as a yttrium-barium-copper oxide, e.g., YBa 2 Cu 3 O x (x being well known to those skilled in the art), or from thallium-based superconductive materials such as a t
- the superconductive tape preferably includes Bi-2223 which can be of any composition suitable in achieving an eventual superconductive tape, e.g., a composition of Bi 1.9 Pb 0.4 Sr 2 Ca 2.2 Cu 3 O 10+x where x is less than about 1 is especially preferred. Other minor variations in precise composition may be suitable.
- M is neodymium (Nd), dysprosium (Dy), erbium (Er), thulium (Tm), gadolinium (Gd), samarium (Sm), europium (Eu), ytterbium (Yb), holmium (Ho) or mixtures thereof, La 2 ⁇ x Sn x CuO 4 , doped with fluorine, YBa 2 Cu 3 O x doped with fluorine, EuBa 2 (Cu 1 ⁇ y M y ) 3 O x where M is chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni) or zinc (Zn), and BaKBiO 3 .
- the well-aligned nuclei of the Bi-2223 phase (with the ab planes perpendicular to the compressive stress) will be favored thermodynamically, and thus grow faster.
- the well-aligned grains are thermodynamically more stable than the poorly aligned grains, the well-aligned grains will grow by consuming the poorly aligned grains if the Bi-2223 phases are already formed. Both of these will lead to higher amounts of texture.
- the compressive stress will prevent the decrease in oxide core density during the annealing. The J c values of these tapes sintered under uniaxial pressure were significantly higher.
- the superconductive tape of the present invention includes a metallic tube or sheath that can generally be of any metal that is chemically compatible and inert with the oxide superconductive material.
- silver is the preferred metal for the tape although silver alloys such as an alloy of silver and gold or silver and those elements which provide additional stiffness, such as aluminum, magnesium, hafnium, titanium, holmium and the like by oxide dispersion strengthening (i.e., ODS-Ag alloys), gold and gold alloys as well as a gold- or silver-plated metal.
- Other noble metals such as platinum may also be used as the casing or sheath.
- a metal sheathed, e.g., a silver sheathed, superconductive oxide precursor is formed by inserting the desired superconductive oxide precursor mixture into a metal tube and such a precursor filled metal tube is rolled or otherwise reduced in size to yield a superconductive oxide precursor tape.
- a metal sheathed, e.g., a silver sheathed, superconductive oxide precursor is formed by inserting the desired superconductive oxide precursor mixture into a metal tube and such a precursor filled metal tube is rolled or otherwise reduced in size to yield a superconductive oxide precursor tape.
- Preparation of such a precursor material is well known to those skilled in the art.
- a pretreatment of the starting precursor material is generally conducted for best results.
- Such a pretreatment can include heating at temperature between about 810° C. and about 840° C., preferably from about 825° C. and about 835° C., more preferably about 830° C., for periods of time from about 1 day to about 3 days at ambient pressure under an atmosphere including a minor portion of oxygen (i.e., less than about 50 percent by volume oxygen), generally from about 5 to about 20 percent by volume oxygen, remainder an inert gas such as argon or nitrogen.
- the atmospheric composition may be varied for optimal results depending upon the particular superconductive oxide material used.
- the oxygen preferably makes up about 10 percent by volume of the atmosphere during the pre-annealing. Other compositions may require or prefer another oxygen content.
- the superconductive tape can next be pressed under an large pressure of about 1 GPa to about 3 GPa at room temperature (about 25° C.). This is carried out to reduce any voids or pores present within the sample being processed. These voids or pores may be caused at least partially by the pretreatment process.
- the superconductive tape is annealed under a low compressive uniaxial pressure of about 4 MPa to about 8 MPa at elevated temperatures of between about 810° C. and about 840° C., preferably from about 825° C. and about 835° C., more preferably about 830° C., for periods of time from about 5 to about 10 days, preferably about 7 days, under ambient air or under an atmosphere including an oxygen partial pressure of about 0.14 atmospheres (atm), with the remainder of an inert gas such as nitrogen or argon.
- a low compressive uniaxial pressure of about 4 MPa to about 8 MPa at elevated temperatures of between about 810° C. and about 840° C., preferably from about 825° C. and about 835° C., more preferably about 830° C., for periods of time from about 5 to about 10 days, preferably about 7 days, under ambient air or under an atmosphere including an oxygen partial pressure of about 0.14 atmospheres (atm), with the remainder of an inert gas such as nitrogen or arg
- the oxygen partial pressure is maintained between about 0.11 atm and 0.21 atm during this stage.
- a superconductive powder of nominal composition Bi 1.9 Pb 0.4 Sr 2 Ca 2.2 Cu 3 O 10+x where x is less than about 1 was inserted into a silver tube of diameter about 1 centimeter (cm), the tube end was sealed and the tube was reduced in size by rolling to about 0.15 millimeter (mm) in thickness and about 1.8 mm in width forming an oxide superconductor precursor tape.
- the precursor tape was pre-annealed by heating under an atmosphere of about 10 percent by volume oxygen, remainder nitrogen, from room temperature to about 830° C. at a rate of about 1° C. per minute, holding at 830° C. for about 35 hours and cooling down to room temperature at a rate of about 1° C. per minute.
- the sample was then cold-pressed (room temperature) at about 3 gigapascals (GPa). Then, the sample was annealed under a low uniaxial compressive force of about 5 megapascals (MPa) by heating under an atmosphere of air (with an oxygen partial pressure of about 0.14 atm), from room temperature to about 830° C. at a rate of about 1° C. per minute, holding at 830° C. for about 153 hours and cooling down to room temperature at a rate of about 1° C. per minute.
- the apparatus shown in FIG. 1 was used to apply the uniaxial pressure.
Abstract
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US09/249,476 US6195870B1 (en) | 1998-02-13 | 1999-02-12 | Compressive annealing of superconductive tapes |
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US7471798P | 1998-02-13 | 1998-02-13 | |
US09/249,476 US6195870B1 (en) | 1998-02-13 | 1999-02-12 | Compressive annealing of superconductive tapes |
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090018023A1 (en) * | 2005-04-06 | 2009-01-15 | Sumitomo Electric Industries, Ltd. | Method of manufacturing bismuth-based oxide superconductor and superconducting wire |
US20100087324A1 (en) * | 2008-10-06 | 2010-04-08 | Flueekiger Rene | Procedure of densifying filaments for a superconductive wire |
US20100248969A1 (en) * | 2007-01-11 | 2010-09-30 | Sumitomo Electric Industries, Ltd. | Oxide superconducting wire, superconducting structure, method of producing oxide superconducting wire, superconducting cable, superconducting magnet, and product incorporating superconducting magnet |
US8592346B2 (en) | 2010-08-02 | 2013-11-26 | The Texas A&M University System | Textured powder wires |
CN105702388A (en) * | 2016-04-25 | 2016-06-22 | 西北有色金属研究院 | Heat processing method of Bi-2212 superconducting wire/strip material |
Citations (4)
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US5223478A (en) * | 1991-05-30 | 1993-06-29 | Westinghouse Electric Corp. | Hot isostatic processing of high current density high temperature conductors |
US5552376A (en) * | 1991-07-24 | 1996-09-03 | Sumitomo Electric Industries, Ltd. | Method of preparing bismuth oxide superconducting wire |
US5639714A (en) * | 1988-08-29 | 1997-06-17 | Sumitomo Electric Industries, Ltd. | Method of producing oxide superconductor |
US5674814A (en) * | 1994-11-14 | 1997-10-07 | University Of Chicago | Synthesis of increased-density bismuth-based superconductors with cold isostatic pressing and heat treating |
-
1999
- 1999-02-12 US US09/249,476 patent/US6195870B1/en not_active Expired - Fee Related
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5639714A (en) * | 1988-08-29 | 1997-06-17 | Sumitomo Electric Industries, Ltd. | Method of producing oxide superconductor |
US5223478A (en) * | 1991-05-30 | 1993-06-29 | Westinghouse Electric Corp. | Hot isostatic processing of high current density high temperature conductors |
US5552376A (en) * | 1991-07-24 | 1996-09-03 | Sumitomo Electric Industries, Ltd. | Method of preparing bismuth oxide superconducting wire |
US5674814A (en) * | 1994-11-14 | 1997-10-07 | University Of Chicago | Synthesis of increased-density bismuth-based superconductors with cold isostatic pressing and heat treating |
Non-Patent Citations (21)
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090018023A1 (en) * | 2005-04-06 | 2009-01-15 | Sumitomo Electric Industries, Ltd. | Method of manufacturing bismuth-based oxide superconductor and superconducting wire |
US20100248969A1 (en) * | 2007-01-11 | 2010-09-30 | Sumitomo Electric Industries, Ltd. | Oxide superconducting wire, superconducting structure, method of producing oxide superconducting wire, superconducting cable, superconducting magnet, and product incorporating superconducting magnet |
US20100087324A1 (en) * | 2008-10-06 | 2010-04-08 | Flueekiger Rene | Procedure of densifying filaments for a superconductive wire |
US8372784B2 (en) * | 2008-10-06 | 2013-02-12 | Bruker Biospin Ag | Procedure of densifying filaments for a superconductive wire |
US8592346B2 (en) | 2010-08-02 | 2013-11-26 | The Texas A&M University System | Textured powder wires |
CN105702388A (en) * | 2016-04-25 | 2016-06-22 | 西北有色金属研究院 | Heat processing method of Bi-2212 superconducting wire/strip material |
CN105702388B (en) * | 2016-04-25 | 2017-03-29 | 西北有色金属研究院 | A kind of heat treatment method of 2212 superconducting wires/strips of Bi |
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